Advances in Antenna Designs for UHF RFID Tags Mountable on Conductive Items

The design of antennas for metal-mountable radio-frequency identification tags is driven by a unique set of challenges: cheap, small, low-profile, and conformal structures need to provide reliable operation when tags are mounted on conductive platforms of various shapes and sizes. During the past decade, a tremendous amount of research has been dedicated to meeting these stringent requirements. Currently, the tag-reading ranges of several meters are achieved with flexible-label types of tags. Moreover, a whole spectrum of tag-size performance ratios has been demonstrated through a variety of innovative antenna-design approaches. This article reviews and summarizes the progress made in antennas for metal-mountable tags, and presents future prospects.